1. Field of the Invention
The invention relates to a control for a motor drive of a device that is movable, in particular, drivable, by muscle power as well as, in a supporting function, by the motor drive, comprising an apparatus, detecting kinematic parameters of the moving device and generating motor drive control signals, for adjusting a degree of support action for the muscle power drive by means of the motor drive based exclusively on the detected kinematic parameters.
2. Description of the Related Art
Drives which are based on muscle power as well as motor power are known from drivable devices, such as bicycles or golf carts. In this connection, the motor drive has a supporting function in that it provides, for example, a portion of the total required driving power which surpasses a basic load to be provided by muscle power. The total required driving power results from the behavior of the user of the drivable device who, for example, wants to accelerate or/and maintain a certain speed under the different drive path conditions that are characterized by different inclines or the ground conditions.
A control, known from WO 05/03096, for a drive based on muscle power as well as motor power for a drivable device is based on a continuous measurement of the applied muscle driving power and a control of the measured driving power to a predetermined value. In the context of this control, the drivable device is adjusted by the motor driving power such that the user feels a constant drive resistance corresponding to this value and, thus, to the basic load.
U.S. Pat. No. 5,664,636 describes a control for an electric auxiliary drive of a pedal-driven vehicle in which the aforementioned apparatus for generating motor drive control signals detects, in addition to the speed of the vehicle, continuously the pedal power. The support action by means of the auxiliary drive is adjusted by means of a stored reference table in which desired driving powers correlated to the driving speed and the pedal power are stored.
Controls of the aforementioned kind in which the generation of motor drive control signals is carried out exclusively by means of the detected kinematic parameters are disclosed in EP 0 734 945 A1 as well as WO 96/32314. The control known from EP 0 734 945 A1 for a motor drive of a bicycle comprises an acceleration sensor which can be embodied by a speed sensor and a differential device. Based on the determined acceleration values, motor drive control signals are generated which provide for a change of the drive support action by the motor drive so that the pedal driving power required during the time period of acceleration of the bicycle is accordingly reduced. For changing the drive support action, the switching ratio of the drive motor operated with pulse width modulation is varied. In the control known from WO 96/32314 the speed of the vehicle driven by muscle and motor driving power is continuously determined and the motor driving power is adjusted according to a stored functional relation between the motor driving power and the speed of the vehicle.
With the present invention, a new control of the aforementioned kind is provided in which the aforementioned kinematic parameters relate to a movement component which is based on the periodic fluctuation of the exerted muscle driving power inherent in the muscle power drive or/and a change of the exerted muscle driving power in reaction to a certain change of the motor driving power or the motor driving speed.
Preferably, the aforementioned apparatus is designed for generating motor driving power control signals according to a desired support or relief of the muscle power drive by means of the motor power drive, wherein the support action can be realized according to a desired proportion of motor power relative to the total driving power or according to an optionally adjustable constant basic load to be provided by the muscle power drive.
In a preferred embodiment of the invention the aforementioned apparatus is designed for determining and evaluating time functions of kinematic parameters and comprises especially an analytical device comprising a differential device for evaluating the time functions. According to this embodiment, a device for detecting travel-time-functions or speed-time-functions could be provided wherein optionally acceleration-time-functions and time functions of higher derivatives can be formed with the aid of the differential device.
The muscle power drive may be, for example, the pedal drive of a bicycle in which a circular drive motion results by actuation of the pedal crank device. According to the conditions of the muscle power generation and transmission in such a drive, the driving power that can be transmitted onto the pedals fluctuates for such a drive such that the driving power has a minimum in the vertical position of the pedal crank and has a maximum in the horizontal position of the pedal crank. According to this fluctuating driving power, the acceleration or/and speed profile of the bicycle powered by a muscle power drive has a periodic component. The amplitudes of the periodic components depend on the average pedaling force.
Such a periodic component also results for a muscle power drive in which a running movement is realized by exerting a pulling or pushing force transmitted, for example, onto a drivable device. According to the power generating and transmission conditions changing with the running movement, a periodic increase and decrease of the pulling or pushing force results, wherein these fluctuations are the greater, because of the increasingly stronger coupling action via the muscle tension, the greater the transmitted average pulling or pushing force.
For generating control signals, the aforementioned apparatus can evaluate the amplitudes of the periodic components of the speed or/and acceleration profiles wherein an average speed or/and acceleration overlaying the periodic component can be taking into account. In this evaluation, the amplitudes are preferably compared to a predetermined stored amplitude wherein the stored amplitude can be selected according to a basic load to be supplied by the muscle power drive.
Inasmuch as the signal generation is carried out with the goal that a certain basic load is to be provided by muscle power, the control signal generation by the aforementioned apparatus can be performed by controlling the amplitude of the periodic component of the detected speed profile to the predetermined amplitude.
In a further embodiment of the invention, the determination of kinematic parameters is based on a predetermined model of the drive behavior of a user of the device who supplies the muscle power. Such a behavior model can be, for example, typical drive movements for certain drive situations, for example, the initial muscle-powered movement when starting to drive the drivable device. In reaction to such an initial driving movement, which can be determined by comparison with correspondingly stored movement courses, control signals for a suitable activation of the motor drive can be generated.
The behavior model is a reaction model which results from certain changes of the drive action by the motor drive, wherein the predetermined changes of the drive, for example, may reside in the slow increase or decrease of the motor driving power or driving speed and wherein the aforementioned apparatus is designed for switching from increase to decrease of the motor driving power or speed when the movement of the driven device decelerates and for switching from decrease to increase when the movement of the driven device accelerates. Such a control is based on the idea that, when, for example, the motor driving power increases, the user is reducing the muscle power correspondingly for the time period for which he desires a support by the motor drive. When the user no longer reduces the muscle driving power to the degree in which the motor driving power increases, an acceleration is caused, and form this it can be deduced that the user finds this motor driving power, that has increased up to the point of acceleration, desirable. In the reverse situation, when the motor driving power decreases slowly, a negative acceleration of the drivable device results when the user no longer increases the muscle driving power accordingly, and, based on this, the aforementioned apparatus can determining that the motor driving power reached at the point where the negative acceleration occurs is the desired motor driving power. In this way, the driving support action desired by the user of the drivable device will be automatically adjusted.